OK, I can see that London does have advantages of scale that is not replicable in other areas.
However - if Further Maths can be taught in a Grammar school down the road from the High School, why couldn't it be taught to those same kids by those same teachers in top set classrooms in the same school? Where late developers and the children of parents who didn't support them to pass the 11+ could also take part?
And if dynamic talented teachers are reluctant to move to deprived areas with a lower density of schools for their professional development etc, then how do Grammars in deprived areas (plenty of deprived areas in Kent) attract talented teachers?
I am not saying that these are not issues, but 'not achieved' doesn't necessarily mean 'not achievable' does it?
Fair point that London schools benefitted from investment and political lobbying. Exactly! Surely that proves the need for investment - the investment that has supported London comps to succeed. That's what schools everywhere need! For pupils of all abilities! (not all London comps are good, of course... but actually lots of Grammar schools add nothing beyond reflecting the ability of the cohort)
As for attracting teachers - I would listen to what teachers most value. And work at providing it.
Anecdotally what my teacher friends and family say is that the workload is enormous, the management too heavy handed and prescriptive and not enough support - in and out of school - for those with additional needs. Oh, and bolshy parents, of kids of all abilities so I doubt Grammars will avoid them.
My brother is a teacher in an area of economic and cultural deprivation. What prompted him to move schools to one an extra 10miles drive away was micro management and heavy handed targets from a 'superhead' with no teaching experience and apparently little liking for kids. My brother is in a subject with an acute recruitment problem, and had been identified in Ofsted reports at 2 different schools as offering inspirational and effective lessons. He lives in an area of deprivation (educationally - nice scenery), has done for 40 years and won't move - it was the school culture instilled by Gove et al that made him move jobs.